I have 2 HX620's and when I had my first one, after a week it started making alot of noise. And I did,nt know what it was, after taking a closer look I found that the sticker that was on the fan came lose and was stuck inside the psu and kept hitting the fan. So I just got it out of the psu and it was quite again. I took the sticker out of the second psu before I even installed it.